1. Field of the Invention
This invention relates to the removal of deposits comprising heavy hydrocarbonaceous materials and finely divided inorganic solids from well surfaces, such as the inside of piping such as well tubing or casing, screens and the near wellbore formation, using an acidic alkyl polyglycoside surfactant composition.
2. Background of the Invention
Mixtures of oil, gas and water are frequently produced from oil fields. Processes for treating such mixtures to produce separate streams of oil, gas and water are well known. Typically the oil is separated and recovered as a product; the gas may be separated and recovered as a product; or, alternatively, the gas may be injected into a gas cap above an oil-bearing zone, into an oil-bearing zone or the like as recovered or as a miscible injectant which comprises the produced gas adjusted by the addition of nitrogen, carbon dioxide, hydrocarbons containing from one to about five carbon atoms and the like to adjust the specific gravity of the gas to produce the miscible injectant. The water may be recovered for injection or disposal by other means as known to those skilled in the art. The separation is frequently accomplished in large settling tanks where the oil, gas and water are allowed to gravimetrically separate.
In many instances, the mixture of oil, gas and water is passed to central processing facilities for separation with the oil being recovered as a product and with the gas being either wholly or partially recovered as a product also. In some instances, the gas is distributed to injection wells and injected; and, in some fields, the water is similarly recovered, passed to injection wells and injected into the formation for the disposal of the water, for secondary oil recovery and the like.
It has been found, when such operations are conducted, especially when corrosion inhibitors are used in the lines leading from the wells to the central processing facility and the like, that, over a period of time, deposits of heavy hydrocarbonaceous materials and finely divided inorganic solids deposit on the inner surfaces of the water, and water and gas, injection well tubing and casing, in the near wellbore formation, in the settling tanks and the like. These deposits typically comprise finely-divided inorganic particles such as produced solids which may include hydraulic fracturing proppant, formation sand, formation fines and precipitates of materials such as iron sulfide, carbonates such as limestone and the like. These particles become coated with corrosion inhibitor or other surfactant materials and subsequently accumulate additional quantities of heavy hydrocarbonaceous material in the flowlines, settling tank and the like. These deposits are difficultly removed from any surface and particularly from the inner surfaces of wells, the near wellbore formation and the like. The deposits are detrimental to continued operations in wells for a number of reasons. It has been found that they shelter bacteria which generate corrosive sulfides and other compounds beneath the deposits and in contact with the pipe. This results in accelerated corrosion of the pipe surfaces, the formation of pits and eventual failure of the pipe. The replacement of pipe is expensive. Such deposits may be partially removed with organic solvents such as mixtures of diesel oil and xylene, but such solvents do not dissolve the particulates and accordingly are not effective to remove heavy deposits. Such deposits in wells are particularly common in wells which are used for alternating water and gas injection and in zones of restricted flow in production wells such as gravel packs and the like.
Such deposits may also plug production wells. The deposits in production wells may be formed by a combination of production treatment chemicals, such as scale inhibitors or corrosion inhibitors, oil and finely divided particles which may be produced with fluids from a producing formation or otherwise present in the wellbore. The deposits in producing wells may plug or reduce the flow through the near wellbore formation, gravel packs and the like.
In view of the difficulties created by these deposits, a continuing search has been directed to the development of a composition and a method for the removal of such deposits.